Conventionally, there is known an in-vehicle radar apparatus that radiates a radar wave (e.g., laser wave, millimeter wave, and the like) as a transmission wave at a specified interval across a specified angle around a vehicle. The in-vehicle radar apparatus receives a reflected wave to detect an object around the vehicle.
This type of in-vehicle radar apparatus is applied to so-called automatic cruise control. That is, the in-vehicle radar apparatus detects whether or not an obstacle exists in the vehicle's traveling direction. When an obstacle is found, the in-vehicle radar apparatus provides control to generate an alarm for a driver. The in-vehicle radar apparatus mounted in a vehicle detects a vehicle (preceding vehicle) that is located ahead of the vehicle and travels along the same lane as for the vehicle. In this manner, the in-vehicle radar apparatus controls the vehicle speed so as to keep a constant distance to the preceding vehicle.
An objective is to specify the preceding vehicle among various objects recognized based on the radar wave. To achieve this, it is necessary to highly accurately recognize a road shape ahead of the vehicle.
There is known an apparatus that recognizes a road shape (e.g., see patent document 1). As shown in FIG. 8, the apparatus extracts a roadside object (e.g., acoustic insulation barrier or guard rail) from various recognized objects. The apparatus calculates an approximate curve that represents a disposition state of the extracted roadside object to estimate the road shape.
However, the apparatus described in patent document 1 newly recalculates a disposition state of the roadside object only based on a detection result from a one-time operation of the radar apparatus each time it operates. When the roadside object is incorrectly detected due to a sporadic noise and the like, the road shape recognition is greatly influenced.                Patent document 1: JP-2001-256600 A        